In order to generate a bootable ipxe.iso for booting from coreos-ipxe-server run it with server address and profile name parameters as follows:
WD=$(mktemp -d) # Working directory which will be attached as Docker volume to the container and where the genereated ipxe.iso will be placed after being generated.
docker run --rm -ti -v $WD:$WD -e WD=$WD ipxe_builder ./generate_image.sh -u <server_address> -p <profile_name>
Options: -u BASE_URL Address of the iPXE server. -p profile Name of the coreos-ipxe-server boot profile. -v Super verbose, for debugging. -h This :-)